1. Field of the Invention
This invention relates to liner hangers, methods for hanging a liner casing in a well bore and methods for manipulating a liner casing during a cementing operation.
More specifically, the present invention concerns apparatus and methods to set a liner hanger and the removal of the setting tool with all of the hanger setting mechanisms retained within the retracted setting tool. State of the art liner hanger assemblies leave a portion of the valuable and expensive hanger setting mechanism permanently cemented in the borehole along with the hanger.
2. Background
In well drilling and completion operations, after the borehole is drilled, a tubular liner casing is positioned in the well bore and the annulus between the liner casing and well bore is filled with cement. The liner casing cementing operations are conducted by running the liner casing in the well bore by means of a setting tool and a drill string where the setting tool interconnects the drill string and the liner casing.
U.S. Pat. No. 5,181,570 for example, teaches a liner setting process wherein the liner hanger which is attached to the upper end of the liner casing is set in the well bore at a desired location so that the weight of the liner casing is supported by the liner hanger. Prior to the cementing operation, the setting tool is released from the hanger assembly by shearing shear screws then backing off an internal running nut that secures the setting tool to the hanger. Once the drilling operator is satisfied that the setting tool is in fact released from the hanger and that the entire weight of the casing is suspended from the hanger, the setting tool torque housing is then re-engaged to the hanger. Cement is subsequently introduced through the drill string and through the liner casing and flows out a cement shoe which is attached to the bottom of the liner casing and having a multiplicity of orifices through which cement is introduced into the annulus between the liner casing and the well bore. After filling the annulus with cement, the setting tool is pulled from the liner casing hanger assembly and retrieved with the drill string when the drill string is withdrawn.
To improve the cement bond between the liner casing and the well bore, If the suspended liner casing can be reciprocated and or rotated during the cementing operation. This movement will greatly assist in a uniform distribution of the cement in the annulus and proper displacement of the drilling mud. In order to rotate the liner casing during the cementing process, the drill string must be selectively engaged to the liner casing through the liner hanger so that rotation of the drill string causes the liner casing to be rotated relative to the liner hanger until after the cementing operation is complete. The drill string and setting tool is subsequently disengaged from the liner hanger and is pulled out of the borehole leaving the casing cemented in place.
It goes without saying that the setting operation requires considerable care because once the cementing operation is complete, the liner casing cannot be removed or repositioned. Moreover, if the setting tool fails to disengage prior to the cement hardening, the drill string could also be cemented in place. Such malfunctions can result in the loss of expensive drilling equipment, or worse, the loss of the well.